In recent years SnO2 has attracted a lot of interest because of its outstanding electrical, optical and electro-chemical properties and these properties has enabled the application of SnO2 in solar cells, catalytic support materials, transparent electrodes and solid state chemical sensors. Very recently, nano-crystalline SnO2 has gained prominence in technological field due to its interesting electrical and optical properties arising out of large surface-to-volume ratio, quantum confinement effect. The synthesis of metal oxide nanoparticles using plant extract is an alternative method to other chemical and physical methods which has environmental toxicity or biological hazards. Hence it is a challenge to find cost effective, non-toxic natural metal oxide nanoparticles and to synthesize them. Plant extracts will act both as reducing and capping agents in the synthesis of nano particle. In the present study SnO2 nanoparticles were synthesized by using ethanolic extract of the plant Stevia rebaudiana. The tin oxide nanoparticles thus formed was characterized by UV, PL and SEM. The antibacterial activities of SnO2 nanoparticles were studied by using Klebsiella pneumoniae and Staphylococcus aureus.